The present embodiments relate to clinical assessment of spinal stability, and more particularly, to a method and system for tracking, stabilizing, and reporting motion between vertebrae.
One of the primary functions of the spine is to protect the spinal cord and associated neural elements, as well as, mechanically support the upper body so that a person can perform the desired activities of daily living. When these mechanical functions are compromised by trauma, disease, or aging, the individual can experience pain and other symptoms. Millions of people suffer from disorders of their spine. Back disorders are a leading cause that prevents individuals from working productively in society. As part of the diagnosis and treatment of these individuals, clinicians need to know if the motion in the spine is abnormal.
The spine consists of 26 bones call vertebrae. Vertebrae are normally connected to each other by a complex arrangement of ligaments. A large number of muscles also attach to these vertebrae and create motion required by the individual. Vertebrae have complex geometries and are separated from each other by a structure called the intervertebral disc. Several research studies have shown that if vertebrae are fractured, if ligaments between vertebrae are damaged, or the intervertebral disc between vertebrae is damaged, then the motion between the vertebrae can be altered. When diagnosing and treating a patient with a spinal disorders clinicians need to know if motion between vertebrae is abnormal or not, since any abnormalities in motion can help the clinician understand what part of the spine has been damaged.
Clinicians use physical tests and imaging studies to determine if motion in the spine is abnormal. The ability to correctly identify abnormalities in motion (the sensitivity), and the ability to correctly determine that there is no abnormality (the specificity) of most common clinical tests are either not known, or have been shown by scientific studies to be unreliable or inaccurate in many patients. One of the most common clinical imaging studies used to assess motion in the spine is simple radiographs. In some cases, the clinician compares radiographs taken with the person in two or more different positions, to assess motion in the spine. A single static image can show if there is any misalignment of the spine, but the single image cannot be used to determine if there is abnormal motion in the spine. Comparing radiographs taken of the patient in two or more positions can be difficult and scientific studies have shown this technique to have significant limitations.
To be of clinical value, a diagnostic test must be reliable, easy to interpret, and ideally should be non-invasive and relatively fast. Currently, the most accurate method for measuring motion between vertebrae in living subjects, is to surgically implant metal markers into the vertebrae. The technique is commonly referred to as Roentgen Stereophotogrammetric Analysis (RSA). With RSA, radiographic images are obtained with the patient in two or more different positions. The radiographic images must be taken with the patient located within a geometric calibration frame that allows the spatial coordinates of the images to be calculated. The position of the metal markers can then be measured and compared between images. Radiographs are also usually taken in two different planes, allowing for three-dimensional motion measurements. Although this method can be accurate, it is invasive because it requires surgical implantation of markers. In addition, it is time consuming to analyze the image to measure motion of the markers. Although, this method has been used in laboratory and clinical research studies, it is not known to be used in routine clinical practice.
Another method that has been used to measure motion between vertebrae in the spine involves combining geometric information obtained from a computed tomography (CT) study of the spine with information from a fluoroscopic imaging study of the spine. By knowing the actual three-dimensional geometry of an object, it is possible to estimate two-dimensional motion from fluoroscopic imaging data. Although this method is non-invasive, it does require a CT examination and substantial post-processing of the data. It is not a method that could be readily used in routine clinical practice. However, this method has been used in several published laboratory studies, mostly related to motion around total joint replacements.
Accordingly, a reliable and accurate method to assess motion in the spine that can be used in clinical practice for overcoming the problems in the art is desired. Such a method could also be useful in research studies to develop better methods for diagnosing and treating patients with spinal disorders.